Cypermethrin induced physiological and metabolic changes in susceptible and resistant populations of Spodoptera litura (Fabricius)

Spodoptera litura (Lepidoptera: Noctuidae) is one of the most destructive insect pests. Insecticides remain the principal management tool to control this pest. However, indiscriminate use of insecticides has resulted in the development of resistance to a variety of insecticides in S. litura. Cypermethrin, a synthetic pyrethroid, is commonly used in pest management. In addition to the mortality produced by cypermethrin, S. litura may suffer a range of sublethal consequences when exposed to low or sublethal levels. This study investigates the effect of cypermethrin exposure on nutritional physiology, digestive, detoxifying, and antioxidant enzymes of lab-selected susceptible (Unsel-Lab) and resistant (CYP-Sel) populations of S. litura. Our findings demonstrated that cypermethrin exposure has a considerable impact on the nutritional physiology of S. litura, as revealed by altered nutrient assimilation and utilization, alongside varying responses in digestive enzymes. In the CYP-Sel population, activity levels of key digestive enzymes- α-amylase, α-glucosidase, ß-glucosidase, α-galactosidase, ß-galactosidase, lipases, and proteases- decreased by 69.30, 81.40, 49.18, 86.36, 73.94, 70.50, and 72.34%, respectively, compared to the control of Unsel-Lab population. Furthermore, detoxification enzymes including mixed-function oxidase (by 1.87 times), glutathione-S-transferase (by 1.71 times), and esterases (by 2.86 times) showed considerably increased activity in CYP-Sel population as compared to Unsel-Lab population, indicating an adaptive response to detoxification processes. Antioxidant enzyme activity, including SOD (increased by 19.66%) and CAT (decreased by 26.19%), changed significantly, indicating oxidative stress caused by cypermethrin. The study gives useful information for developing pest management strategies that reduce the unexpected impacts of chemical exposure.